To critics who object to making ethanol fuel out of grain, Larry Lehr, of Waco, has an ecology-minded answer: Run it through a cow first.

Lehr, who teaches environmental science at Baylor University, is planning to build a manure-to-ethanol demonstration plant at a model dairy that Tarleton State University is building in Stephenville.

The project will be designed to turn the manure from the dairy’s 400 cows into pure ethanol that can be blended with gasoline as fuel. Unlike conventional ethanol, it would require no fossil fuels to produce. The distillery would run on methane from a manure digester.

The byproduct of the distillations would include concentrated nitrogen and phosphorus fertilizer, which could be packaged and sold. And carbon dioxide emissions from the process might even be used to grow algae that could be turned into biofuel.

But the main purpose is to develop systems that dairy farmers can buy to turn their herds’ waste into a profitable commodity instead of allowing it to pollute streams, Lehr said.